The invention is directed to a planar waveguide Bragg lens.
Planar optical components frequently require lenses which collimate the light of a laser diode or focus the collimated light. A typical example is an integrated optical spectrum analyzer in which the light emerging from the laser diode is collimated by means of a first lens and then bent by an ultrasonic Bragg cell and finally focused on a row of detectors with a second lens such as the Fourier lens. Since the deflection angle is proportional to the frequency, it is possible to associate a specific frequency band with each detector element. As waveguides lenses, grating lenses, in the form of Bragg lenses are of a particular interest because they can be manufactured in a conventional planar technology in a simple and reproduceable fashion and because they exhibit a high bending or deflection efficiency.
Up to the present time, planar waveguide Bragg lenses were only manufactured with a straight grating structure. However, this straight grating structure has a high bending or deflection efficiency only for a very small acceptance angle range.